1. Field of the Invention
The present invention relates to a mask for forming a pattern on a substrate in a deposition apparatus and a method for manufacturing a display device using the same, and more particularly, to a mask which is applied to Plasma Enhancement Chemical Vapor Deposition (PECVD) for forming a passivation layer of an Organic Light Emitting Diode (OLED) display.
2. Discussion of the Related Art
Generally, vapor deposition is largely categorized into Physical Vapor Deposition (PVD) and Chemical Vapor Deposition (CVD).
A difference between the PVD and the CVD exists according to a process that is performed when a deposited material is changed from a gaseous state to a solid state. Particularly, there is a clear difference in that the PVD requires a vacuum environment, but the CVD is sufficiently performed even at an environment of tens to hundreds torr or a normal pressure environment. In this case, the CVD requires an environment of a far higher temperature than that of the PVD.
As examples of the PVD, there are sputtering, E-beam evaporation, thermal evaporation, Laser Molecular Beam Epitaxy (L-MBE), and Pulsed Laser Deposition (PLD). The reason that such processes may be included in the PVD is because when a material to be deposited is deposited on a substrate, an operation of changing a gaseous state to a solid state accompanies physical change.
As examples of the CVD, there are Metal-Organic Chemical Vapor Deposition (MOCVD) and Hydride Vapor Phase Epitaxy (HVPE). The CVD conveys raw materials in a gaseous state, but the raw materials have a chemical reaction on the surface of a substrate.
The CVD process is largely categorized into three processes according to the reaction condition of a reaction chamber (for example, according to the degree of vacuum).
First, Atmospheric Pressure Chemical Vapor Deposition (APCVD) induces a reaction with energy due to heat when the degree of vacuum of a reactor is an atmospheric pressure.
Second, Low Pressure Chemical Vapor Deposition (LPCVD) induces a reaction with energy due to heat when the degree of vacuum of a reactor is a low pressure.
Third, PECVD induces a reaction with energy due to heat and plasma generated by a Radio Frequency (RF) power when the degree of vacuum of a reactor is a low pressure.
FIGS. 1 and 2 are exemplary views illustrating a state where a substrate and a mask are aligned in a PECVD apparatus.
The PECVD provides one or more compound gases, which includes an element configuring a thin film material to be formed, onto a substrate and thus forms a desired thin film by a chemical reaction that is performed in a gaseous state or a substrate surface.
Such a PECVD apparatus includes a vacuum chamber (not shown) where a chemical reaction is performed and a stage that is horizontally disposed in the vacuum chamber for supporting a substrate 10.
The PECVD apparatus is generally used without a separate mask when a thin film is formed on a substrate, but may use a mask 20 of FIG. 1, for example, when a passivation layer of an Organic Light Emitting Diode (OLED) display is formed.
In the PECVD apparatus, as illustrated in FIG. 1A, the mask 20, which is used when forming the passivation layer of the OLED display, includes a mask pattern 22 formed inside a frame 21. The substrate 10 is disposed under the mask 20 and on a stage in a shape where the substrate 10 is formed in a direction from an upper portion to a lower portion.
The material of the frame 21 may be ceramic or metal. When the material of the frame 21 is metal, sagging of the mask may be minimized through stretch.
However, as illustrated in FIG. 1B, because the mask 20 is formed in a right angular shape at the edge of the frame 21 without any step, a shadow effect (illustrated with dot lines in FIG. 1B) may occur on the substrate or near the mask pattern region depending on the thickness of raw materials. The shape of the shadow may vary.
That is, as illustrated in FIG. 1B, when the lower portion of the mask 20 is stretched, such a shadow effect may seriously occur due to the thickness of the frame 21.
As illustrated in FIGS. 2A and 2B, when the upper portion of the mask 20 is stretched, the mask 20 is modified when the substrate 20 is adhered to the mask 20, causing a film-penetration.
The mask 20 that is used in the above-described PECVD process has limitations in that a shadow effect may seriously occur at the boundary between the frame 21 and the mask pattern 22. Also, a film-penetration may occur at the masking region when the mask 20 is lifted as the stage is raised.